If the base concept is making permanent the translators, then any addition would likely have to be restricted to the equivalent of a Class A and subject to existing stations. Probably any permanent allocation would have to guarantee a safety zone to existing stations in the event they had to move transmitter sites... something like a 10 km radius, for example.
A new station grant or an upgrade that increases value is not generally capitalized beyond costs. that is why stations that have had the same owner since founding don't have a large value on the books as they did not pay for the intangible value of the license other than small fees and legal costs.
Any major station that wanted a good FM signal likely has a full B or C they can use. The idea of "rescue" plans is to allow stations that would prefer shutting their AM down if the translator were guaranteed permanence. Right now, a move in power, height or location by an A, B or C can force a translator to move frequency, transmitter site or to even close.
The FCC has made major moves of UHF TV to accommodate cellular operators using "public interest" as the reasoning. I see no reason why t hey could not do the same for AM's by rearranging the FM band. In fact, with cellular being a paid service, granting improvements to radio which is a free service seems to be even more in the interest of the consumer.